Fungicide programmes for barley

Focused on the main spray timings, use this information to design fungicide programmes to optimise control and manage fungicide resistance risks in barley.

Low levels of resistance in some popular varieties, as well as the unpredictability of disease, mean fungicide use is relatively high in barley crops. However, such use puts selection pressure on pathogens, making fungicide resistance more likely to occur. These steps will help you maintain sustainable levels of control.

Resistance management should be considered throughout the spray programme.

Yield potential in barley is determined early in the season. Consequently, early disease control is relatively important, but season-long protection maximises grain storage capacity. There are four key spray timings, but T1 and T2 sprays adequately protect most crops.

Autumn/winter

Mildew is the main disease at this stage, although brown rust, rhynchosporium and net blotch may occasionally cause concern. However, applications at this stage rarely have a yield benefit and encourage fungicide resistance to develop. They are only necessary if extensive disease affects overwintering capability in poorly tillered crops. Use a specific mildewicide where mildew is the target. To minimise selection for resistance, use different modes of action to those planned for later in the season.

T0: GS23–29 late tillering, early spring

Yield responses to fungicides are highly variable at this timing. Only spray if overwintering disease levels are high in susceptible varieties.

Mildew, brown rust, rhynchosporium and net blotch are the main diseases to consider at this timing. Use a specific mildewicide for mildew control. To minimise selection for resistance, use different modes of action to those planned for later in the season.

T1: GS30–32, stem extension

This is the main timing in winter barley, with a 60% response to fungicides achievable. Treatment helps maximise survival of formed tillers and spikelets, increasing final grain numbers. Six-row barley responds similarly to two-row barley.

Rhynchosporium, net blotch, mildew, eyespot and brown rust are the main diseases to consider at this timing. An azole in a mixture with a strobilurin or SDHI will control most target diseases. However, if brown rust is a particular threat, use a strobilurin. Use mixtures with different modes of action that give similar efficacy against the diseases present, where possible. Cyprodinil is an alternative mode of action for net blotch and rhynchosporium control. Add a multisite to protect the other modes of action. Folpet is the only available multisite for barley.

T2: GS39–59, flag leaf and ear emergence

About 40% of the fungicide yield response can come from this timing. Greater yield responses often occur in years with a later harvest. It is the key timing for ramularia control, with GS45–49 (awns peeping) being the optimum timing for this disease. Brown rust and net blotch are also targets, along with rhynchosporium in wetter western regions and in wet summers.

Applications around flag leaf emergence can reduce spikelet mortality during booting and extend canopy duration. Applications, especially later ones towards the end of booting, can also result in a higher thousand-grain weight (TGW). If there are high levels of late-developing net blotch and brown rust, use later applications, but use earlier applications when disease pressure (especially rhynchosporium) is generally high. When an early application is used, an additional application may be required at or before GS59.

Use an azole in a mixture with a strobilurin or SDHI to control most target diseases. If brown rust is a particular threat, use a strobilurin. Few effective options remain for ramularia.

Be aware that eradicant mildew fungicides can reduce green leaf area. The latest application time for many fungicides in malting crops is the start of ear emergence. Product choice for feed barley is limited once ears have emerged. Check product labels to determine whether they are suitable for use when the T2 is delayed.

Use mixtures with different modes of action that have activity against the diseases present. Alternate modes of action, compared with the T1 spray, where possible. Use a different azole to that used at T1 and add a multisite to protect the other modes of action. Folpet is the only available multisite for barley.

T3: after GS59

Avoid sprays after GS59, as they seldom give an economic yield benefit and few products are approved. Where fusarium head blight is a concern, use non-chemical control measures. In very high-risk situations, consider a spray during early flowering (GS63–65), subject to the latest timings on the label.

Fungicides can provide early protection of developing tillers and spikelets and protect grain development and filling. One or two sprays, applied at T2 and/or T1, protect most crops. Sowing date, variety and disease risk influence the optimum spray timing. As usual, use mixtures of modes of action in which components have activity and similar efficacy on the target disease.

T0: GS12–22 (before mid-tillering)

This spray is only required if mildew is present on a susceptible variety. If disease pressure warrants it, use a specific mildewicide.

T1: GS25–31 (late tillering)

This is the main timing for rhynchosporium control, although brown rust, net blotch and mildew are also targets. About 40% of yield response to fungicides comes from this timing. Azoles, strobilurins, and SDHIs are used at this timing, programmes can be cut back in late-sown crops, dry years or where disease levels are low. In late-sown resistant crops, this timing may be omitted altogether. A strobilurin may be especially useful for brown rust control. Mildewicides may be required on susceptible varieties where disease pressure is high. A multisite should always be included. Folpet is the only available multisite for barley.

T2: GS39–59 (flag leaf fully emerged to ear emerged)

This is the main timing for net blotch, brown rust and ramularia control. It also provides some rhynchosporium control. About 60% of yield response to fungicides comes from this timing. Where the T1 spray has been omitted from the fungicide programme, an earlier T2 timing (GS37–39) may be appropriate. GS45–49 (awns peeping) is the optimum time for control of ramularia.

Use an azole or strobilurin with an SDHI and multisite. A strobilurin may be especially useful for brown rust control. Mildewicides may be required on susceptible varieties where disease pressure is high. Few effective options remain for ramularia control: although folpet will have a greening effect, it has not controlled ramularia in fungicide performance trials. Some SDHI+azole mixes may give some control of ramularia, but resistance is patchy. For information on the performance of fungicides, including Revystar XE and Proline, visit ahdb.org.uk/fungicide-performance

Note: the cut off for malting crops for Revystar XE is GS45.

The latest application time for many fungicides in malting crops is the start of ear emergence. Product choice for feed barley is limited once ears have emerged. Check product labels to determine whether they are suitable if T2 is delayed.

Fungicides that have multisite modes of action are at lower risk of resistance and have no recorded instances of resistance in cereal foliar diseases. Folpet is the only available multisite for barley.

Use multisites as a cost-effective mixture partner to protect higher-risk single site-acting fungicides (e.g. azoles and SDHIs) at each application timing.

Plan the programme to maximise use of the most effective multisite options – i.e. make full use of total maximum doses and application numbers (without exceeding them).

Although the use of the chlorothalonil (CTL) is no longer permitted (since 20 May 2020), it is essential to use other multisites, as part of an anti-resistance and disease management strategy.

As folpet has lower efficacy, higher doses are required.

Cereal chemistry changes demand a new approach to disease management. Fiona Burnett (FRAG and SRUC) describes how to weave fungicide options into programmes to protect efficacy and maintain sufficient disease control.